U.S. patent application number 14/034772 was filed with the patent office on 2014-04-03 for liquid crystal display device.
This patent application is currently assigned to Japan Display Inc.. The applicant listed for this patent is Japan Display Inc.. Invention is credited to Akio Tezuka, Saburo WATANABE.
Application Number | 20140092336 14/034772 |
Document ID | / |
Family ID | 50314351 |
Filed Date | 2014-04-03 |
United States Patent
Application |
20140092336 |
Kind Code |
A1 |
WATANABE; Saburo ; et
al. |
April 3, 2014 |
LIQUID CRYSTAL DISPLAY DEVICE
Abstract
Liquid crystal display device preventing brightness reduction of
a backlight even when a recess is formed in a lower frame
accommodating the backlight and a light-emitting diode substrate
mounted with a light-emitting diode is accommodated in the recess.
A backlight includes a reflection member arranged on the back side
of a light guide plate, and the light-emitting diode irradiating
the light guide plate with illumination light from a side portion
of the light guide plate. The recess protruding on the back side is
formed in the lower frame for accommodating and arranging the
light-emitting diode substrate mounted with the light-emitting
diode therein. A part of an end portion of the reflection member
protrudes into a space formed by the recess toward the light
emitting diode. A holding member is arranged between the reflection
member and the lower frame at least to hold the protruding region
of the reflection member.
Inventors: |
WATANABE; Saburo; (Tokyo,
JP) ; Tezuka; Akio; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Japan Display Inc. |
Tokyo |
|
JP |
|
|
Assignee: |
Japan Display Inc.
Tokyo
JP
|
Family ID: |
50314351 |
Appl. No.: |
14/034772 |
Filed: |
September 24, 2013 |
Current U.S.
Class: |
349/58 |
Current CPC
Class: |
G02F 2201/34 20130101;
G02F 1/133605 20130101; G02F 1/1336 20130101; G02F 1/133615
20130101 |
Class at
Publication: |
349/58 |
International
Class: |
G02F 1/1335 20060101
G02F001/1335 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 25, 2012 |
JP |
2012-211081 |
Claims
1. A liquid crystal display device including a liquid crystal
display panel, a backlight irradiating a back side of the liquid
crystal display panel with an illumination light, and a lower frame
accommodating the backlight, wherein the backlight includes a light
guide plate, a reflection member arranged on the back side of the
light guide plate, and a light-emitting diode irradiating the light
guide plate with the illumination light from a side portion of the
light guide plate, a recess protruding on the back side is formed
in the lower frame for accommodating and arranging a light-emitting
diode substrate mounted with the light-emitting diode therein, a
part of an end portion of the reflection member protrudes into a
space formed by the recess toward the light emitting diode, and a
holding member is arranged between the reflection member and the
lower frame at least to hold the protruding region of the
reflection member.
2. The liquid crystal display device according to claim 1, wherein
at least one of the holding member and the lower frame is formed of
an aluminum plate.
3. The liquid crystal display device according to claim 1, wherein
the reflection member and the holding member have a substantially
same shape.
4. The liquid crystal display device according to claim 2, wherein
the reflection member and the holding member have a substantially
same shape.
5. The liquid crystal display device according to claim 1, wherein
the light-emitting diode substrate is fixed to the recess by a
heat-conductive adhesive.
6. The liquid crystal display device according to claim 2, wherein
the light-emitting diode substrate is fixed to the recess by a
heat-conductive adhesive.
7. The liquid crystal display device according to claim 3, wherein
the light-emitting diode substrate is fixed to the recess by a
heat-conductive adhesive.
8. The liquid crystal display device according to claim 1, wherein
a length of a portion of the holding member protruding toward the
light-emitting diode more than the reflection member is within 0.5
mm.
9. The liquid crystal display device according to claim 2, wherein
a length of a portion of the holding member protruding toward the
light-emitting diode more than the reflection member is within 0.5
mm.
10. The liquid crystal display device according to claim 3, wherein
a length of a portion of the holding member protruding toward the
light-emitting diode more than the reflection member is within 0.5
mm.
Description
CLAIM OF PRIORITY
[0001] The present application claims priority from Japanese Patent
Application JP 2012-211081 filed on Sep. 25, 2012, the content of
which is hereby incorporated by reference into this
application.
FIELD OF THE INVENTION
[0002] The present invention relates to a liquid crystal display
device, and specifically to the liquid crystal display device
formed with a recess in a lower frame accommodating a backlight and
with a light-emitting diode substrate mounted with a light-emitting
diode accommodated and arranged in the recess.
BACKGROUND ART
[0003] The liquid crystal display device has been used as a display
device for many electronic devices such as a mobile phone, a
digital still camera, a personal digital assistant, and a medical
equipment. Such a liquid crystal display device includes a
backlight irradiating the liquid crystal display panel with an
illumination light. A typical structure of the backlight employs,
for example, as described in Japanese Unexamined Patent Publication
No. 2006-98500, a configuration including a light guide plate and a
reflection sheet on the back side of the liquid crystal display
panel and arranged with a light-emitting diode serving as a light
source on the side portion of the light guide plate.
[0004] On the other hand, as shown in FIG. 1, the liquid crystal
display device equipped with a large backlight for a medical
application and the like employs a configuration arranged with a
light-emitting diode substrate 6 mounted with a light-emitting
diode 7 on the side portion of the backlight. The liquid crystal
display device shown in FIG. 1 includes a liquid crystal display
panel 1 accommodated in an upper frame 4 and fixed by a mold 3 via
a cushion 2, and a backlight constituted by a light guide plate 9
accommodated in a lower frame 5 and irradiating the back side of
the liquid crystal display panel 1 with the illumination light, an
optical member 10 including a diffusion sheet, prism sheet, and the
like for irradiating the liquid crystal display panel 1 uniformly
with the light guided by the light guide plate 9, a reflection
member 8, and a light-emitting diode 7 irradiating the light guide
plate 9 with the illumination light from the side portion of the
light guide plate 9, wherein the light-emitting diode 7 is mounted
on the light-emitting diode substrate 6 and accommodate and
arranged in a recess 12 protruding on the back side of the lower
frame 5.
[0005] In the liquid crystal display device shown in FIG. 1, the
light emitted from the light-emitting diode 7 enters through a side
face of the light guide plate 9 and diffuses all over the light
guide plate 9. The light about to exit from the back side of the
light guide plate 9 is reflected by the reflection member 8 to be
returned to the inside of the light guide plate 9, and the light
exiting from the front side of the light guide plate 9 is
controlled by the optical member 10 constituted by the diffusion
sheet, the prism sheet, and the like to fall on the entire liquid
crystal display panel 1 uniformly.
[0006] The lower frame 5 provided with the recess 12 for
accommodating and arranging the light-emitting diode substrate 6 is
generally formed of a light metal such as aluminum or a resin. To
form the recess 12 in the lower frame 5, the U-shaped recess 12 as
shown in FIG. 1 is formed by a mechanical bending process or the
like. Due to the limited ability of the process, it is inevitable
that the convex portion has a substantial width.
[0007] The light guide plate 9 and the reflection member 8 need to
be arranged as close to the light-emitting diode 7 as possible to
propagate and reflect the light emitted from the light-emitting
diode 7 without a loss. Accordingly, the light guide plate 9 and
the reflection member 8 in the proximity of the light-emitting
diode 7 partially protrude in a space formed by the recess 12
toward the light-emitting diode 7.
[0008] As a result, the portion of the reflection member 8
protruding into the space formed by the recess 12 bows downward in
the recess 12 over time due to its own weight, forming a gap in
between with the light guide plate 9. When the gap is formed
between the reflection member 8 and the light guide plate 9, as
indicated by a dashed arrow in FIG. 1, a part of the light emitted
from the light-emitting diode 7 and falling downward from the light
guide plate 9 cannot be reflected upward by the reflection member 8
but diffused to the outside. Consequently, an availability of the
light emitted from the light-emitting diode 7 reduces and the
brightness lowers on the whole backlight or locally. Such a gap
between the reflection member 8 and the light guide plate 9 is also
generated by a deformation due to the stress applied when forming
the recess 12 in the lower frame 5 or by a warpage of the lower
frame 5 due to aging.
[0009] Another problem arising when the light-emitting diode 7 is
used as the light source of the liquid crystal display device would
be heating of the light-emitting diode 7. That is, the luminous
efficiency of the light -emitting diode is typically between a few
percent and twenty percent, with a large part of the remaining
energy being converted into heat leading to heat generation. This
heat generation may cause a characteristic degradation of the
light-emitting diode and peripheral devices.
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
[0010] It is an object of the present invention to provide a liquid
crystal display device which can eliminate the problems described
above and prevent brightness reduction of the backlight even when
the recess is formed in the lower frame accommodating the backlight
and the light-emitting diode substrate mounted with the
light-emitting diode is accommodated and arranged in the
recess.
[0011] It is another object of the present invention to provide a
liquid crystal display device which can minimize an effect of the
heat generation even when the light-emitting diode is used as the
light source.
Means For Solving Problem
[0012] To solve the problems described above, a liquid crystal
display device according to the following technical features.
[0013] (1) A liquid crystal display device including a liquid
crystal display panel, a backlight irradiating a back side of the
liquid crystal display panel with an illumination light, and a
lower frame accommodating the backlight is characterized in that
the backlight includes a light guide plate, a reflection member
arranged on the back side of the light guide plate, and a
light-emitting diode irradiating the light guide plate with the
illumination light from a side portion of the light guide plate,
that a recess protruding on the back side is formed in the lower
frame for accommodating and arranging a light-emitting diode
substrate mounted with the light-emitting diode therein, that a
part of an end portion of the reflection member protrudes into a
space formed by the recess toward the light emitting diode, and
that a holding member is arranged between the reflection member and
the lower frame at least to hold the protruding region of the
reflection member.
[0014] (2) The liquid crystal display device described in (1) is
characterized in that at least one of the holding member and the
lower frame is formed of an aluminum plate.
[0015] (3) The liquid crystal display device described in (1) or
(2) is characterized in that the reflection member and the holding
member have a substantially same shape.
[0016] (4) The liquid crystal display device described in any one
of (1) to (3) is characterized in that the light-emitting diode
substrate is fixed to the recess by a heat-conductive adhesive.
[0017] (5) The liquid crystal display device described in any one
of (1) to (4) is characterized in that a length of a portion of the
holding member protruding toward the light-emitting diode more than
the reflection member is within 0.5 mm.
Effect of the Invention
[0018] According to the liquid crystal display device of the
present invention, the recess is formed in the lower frame
accommodating the backlight, a part of the end portion of the
reflection member protrudes into the space formed by the recess
toward the light-emitting diode even when the light-emitting diode
substrate mounted with the light-emitting diode is accommodated and
arranged in the recess, and the holding member is arranged between
the reflection member and the lower frame at least to hold the
protruding region of the reflection member, thereby preventing the
reflection member from bowing. This enables prevention of the
brightness reduction of the backlight caused by the light from the
light-emitting diode diffused without being reflected toward the
liquid crystal display panel.
[0019] Furthermore, because at least one of the holding member and
the lower frame is formed of the aluminum plate or the
light-emitting diode substrate is fixed to the recess by the
heat-conductive adhesive, it is possible to provide a liquid
crystal display device capable of minimizing the effect of the heat
generation even when the light-emitting diode is used as the light
source.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a schematic diagram illustrating a conventional
liquid crystal display device;
[0021] FIG. 2 is a schematic diagram illustrating an embodiment of
a liquid crystal display device according to the present
invention;
[0022] FIG. 3 is a schematic diagram illustrating another
embodiment of the liquid crystal display device according to the
present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0023] A liquid crystal display device according to the present
invention is described below in detail with reference to preferable
examples.
[0024] FIG. 2 is a schematic diagram illustrating an embodiment of
a liquid crystal display device according to the present invention,
and FIG. 3 is a schematic diagram illustrating another embodiment
of the liquid crystal display device according to the present
invention. It should be noted that an illustration of a liquid
crystal display panel and the like is omitted in FIG. 3.
[0025] The liquid crystal display device according to the present
invention including, as shown in FIG. 2, a liquid crystal display
panel 1, a backlight irradiating a back side of the liquid crystal
display panel 1, and a lower frame 5 accommodating the backlight is
characterized in that the backlight includes a light guide plate 9,
a reflection member 8 arranged on the back side of the light guide
plate, 9, and a light-emitting diode 7 irradiating the light guide
plate 9 with the illumination light from a side portion of the
light guide plate 9, that a recess 12 protruding on the back side
is formed in the lower frame 5 for accommodating and arranging a
light-emitting diode substrate 6 mounted with the light-emitting
diode 7 therein, that a part of an end portion of the reflection
member 8 protrudes into a space formed by the recess 12 toward the
light emitting diode 7, and that a holding member 11 is arranged
between the reflection member 8 and the lower frame 5 at least to
hold the protruding region of the reflection member 8.
[0026] For the liquid crystal display device shown in FIG. 2, the
same reference number refers to the same component as in FIG. 1,
and therefore an explanation thereof is omitted or simplified.
[0027] The present invention is characterized by arranging the
holding member 11 between the reflection member 8 and the lower
frame 5 at least to hold the protruding region of the reflection
member 8 to the convex portion 12.
[0028] Thus, by arranging the holding member 11, the holding member
11 supports the reflection member 8 from below, thereby preventing
the reflection member 8 from bowing. As a result, no gap is
generated between the reflection member 8 and the light guide plate
9, and therefore there is no loss of the light entering the light
guide plate 8 from the light-emitting diode 7, which allows for
retaining the brightness of the backlight without lowering it.
[0029] Furthermore, even when a stress is applied to the lower
frame 5 to deform it or when the lower frame 5 warps due to aging
degradation, the holding member 11 still retains the reflection
member 8 without deformation, which also allows for retaining the
brightness of the backlight without lowering it.
[0030] Although a material for the holding member is not especially
limited as long as it has a sufficient strength that does not bow
even when a certain amount of load is applied like resins and
metals, a material containing a light metal such as an aluminum
plate with a high heat conductivity is preferable in order to
control the effect by heat generation from the light-emitting
diode, as described later.
[0031] If a length S of a portion of the holding member 11
protruding toward the light-emitting diode 7 more than the
reflection member 8 is too long, then it is difficult to arrange
the reflection member 8 in the proximity of the light-emitting
diode 7 and the irradiated light from the light-emitting diode is
easily diffused on a surface of the holding member 11, which leads
to the reduction in brightness. For this reason, it is desirable
that the length S of the holding member 11 protruding more than the
reflection member 8 is 0.5 mm or less.
[0032] For the size of the reflection member 8 and the holding
member 11, as shown in FIG. 3, the reflection member 8 and the
holding member 11 may have the substantially same size. The term
"substantially same size" does not mean the precisely same size in
physical terms but it means that both have the approximately same
size and the holding member has the size adequate to control the
bowing of the reflection member. Moreover, as shown in FIG. 3, when
the reflection member 8 and the holding member 11 are larger than
the light guide plate 9 in size, the light that does not directly
enter the light guide plate 9 can also be reflected and fall on the
liquid crystal display panel (not shown) as indicated by the dashed
arrow, thereby improving the availability of the illumination
light.
[0033] Furthermore, when the light emitting diode is used as the
light source as with the liquid crystal display device according to
the present invention, the heat generation due to the light
emission also arises as a problem. This is because the
characteristics (life) of the light-emitting diode and the
peripheral devices may be degraded if the temperature increases in
the device due to the heat generation of the light-emitting
diode.
[0034] Accordingly, in order to control the effect by the heat
generation of the light-emitting diode 7, at least one of the lower
frame 5 and the holding member 11 may preferably be formed of a
highly heat-conductive material, and the material including the
light metal such as the aluminum plate and the resin with the high
heat conductivity may also be used in view of durability and light
weight.
[0035] Furthermore, because the light-emitting diode substrate 6
mounted with the light-emitting diode 7 is susceptible to the
effect of the heat generation of the light-emitting diode 7, the
light-emitting diode substrate 6 is preferably fixed to the lower
frame 5 using a heat-conductive adhesive. As the heat-conductive
adhesive, a resin adhesive using a resin such as epoxy and a
heat-conductive tape using an acrylic adhesive may be used.
[0036] Although the description of the present invention has been
given above based on the embodiments, it is needless to say that
the present invention is not limited to the embodiments but design
modifications can be made without departing from the scope of the
present invention.
Industrial Applicability
[0037] The present invention can provide the liquid crystal display
device capable of preventing the brightness reduction of the
backlight even when the recess is formed in the lower frame
accommodating the backlight and the light-emitting diode substrate
mounted with the light-emitting diode is accommodated and arranged
in the recess. In addition, the invention can provide the liquid
crystal display device capable of minimizing the effect of the heat
generation even when the light-emitting diode is used as the light
source.
* * * * *